The 'Complicated' and 'Wish You Were Here' singer, Avril Lavigne, and her fiance, Chad Kroeger, were gently mocked by her ex and his girlfriend — Deryck Whibley and Ari Cooper

Singer and fashion designer Avril Lavigne's ex-hubby, Deryck Whibley, 32, and his girlfriend, Ari Cooper, opted for an interesting pair of costumes for their Halloween celebrations — they went as Lavigne, 28, and her new fiance, Nickelback's Chad Kroeger, 37, (before his haircut), but cross-dressed, with Whibley as Lavigne and Cooper as Kroeger.

Twitter, Whibley as Lavigne (L) and Cooper as Kroeger (R)

Of course, the costumes might seem slightly odd (perhaps), when you consider that Lavigne is still close to the Sum 41 frontman, Whibley, with whom she still occasionally collaborates. "He's one of my best friends, and we work really well together and we stay in touch," she told Ryan Seacrest of Whibley in 2011. "I think we're very lucky. We've been friends for a really long time and we always will be family. We have a connection. Things are good. I'm really grateful for that."

Regardless of Lavigne's connection with ex Whibley, Kroeger struck back on Twitter with the clever, "Hey Deryck loved the costumes! we were going to dress up as you guys this year but all the parties had celebrity themes haha! -CK."

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